282 JOURNAL OF COSMETIC SCIENCE performance. The authors preferred a full crossover design in order to eliminate habit- related effects and to keep the panel size manageable. The constraint of shorter exposure periods using this regime was not felt to weaken the exercise, as pilot surveys of stain build-up over three months had shown that after six weeks no substantial change in the performance ranking of different pastes occurs. Thus our six-week results indicated that about half the panel were sensitive to the abrasive level in the product. Two distinct sub-groups, however, revealed themselves less so. One group, making up about 20% of the panel, produced visible stain within six weeks whatever paste they were given. This was not related to their declared usage of tea, coffee, red wine, or tobacco. Infrequent brushing, poor technique, or irregular tooth geometry could, however, be contributory factors. The other group, about 30% of the total, developed no visible stain with any of the pastes, including the zero-abrasive paste, during the trial periods. Once again, there was little reason to connect this with drinking or smoking habits, or lack of them. However, it was apparent that these panellists were almost exclusively females in their teens and early twenties. In conclusion, it should be noted that, by directing attention primarily to the concept of dental stain control via prevention instead of removal, a separation of the abrasive efficiency and damage functions becomes possible. Using this test regime, the scope to manipulate abrasive parameters to provide dentifrices exhibiting high physical stain control with low dentine damage potential is greatly increased. ACKNOWLEDGMENTS We thank Dr. P.M. Soparkar (Forsyth Dental Centre, Boston) for his clinical advice and encouragement and Dr. E. Huntington (Unilever Research) for statistical design and data processing. REFERENCES (1) M. Pader, "Surfactants in Oral Hygiene Products," in Surfactants in Cosmetics, M.M. Rieger, Ed. (Marcel Dekker, New York, 1985), pp. 295-296. (2) R. S. Manly, A structureless recurrent deposit on teeth. J. Dent. Res., 22, 479•486 (1943). (3) A. Frandsen, "Mechanical Oral Hygiene Practices," in Dental Plaque Control Measures and Oral Hygiene Practices, H. Loe and D. V. Kleinman, Eds. (IRL Press, Oxford, 1986), pp. 93-116. (4) B. R. Pugh, Toothbrush wear, brushing forces and cleaning performance, J. Soc Cosmet. Chem., 29, 423-431 (1978). (5) P. C. Kitchin and H. B. G. Robinson, How abrasive need a toothpaste be?J. Dent. Res., 27, 501-506 (1948). (6) W.B. Davis, Cleaning and polishing of teeth by brushing. Community Dent. Oral EpidemioL, 8, 237-243 (1980). (7) M. Pader, Oral Hygiene Products and Practice (Marcel Dekker, New York, 1988), pp. 233-239. (8) British Standard Institution, London, Specification for Toothpastes, BS 5136:1981. (9) J. H. Hefferren, A laboratory method for assessment of dentifrice abrasivity,J. Dent. Res., 55, 563-573 (1976).

DENTAL STAIN PREVENTION 283 (lO) 11) (12) (13) (14) (15) D. J. Lamb, R. A. Howell, and G. Constable, Removal of plaque and stain from natural teeth by a low abrasivity toothpaste, Br. Dent. J., 157, 125-127 (1984). R. R. Lobene, Effect of dentifrices on tooth stains with controlled brushing, J.A.D.A., 77, 849-855 (1968). G. K. Stookey, T. A. Burkhard, and B. R. Schemehorn, In vitro removal of stain with dentifrices, J. Dent. Res., 61, 1236-1239 (1982). C.A. Saxton, The effects of dentifrices on the appearance of the tooth surface observed with the scanning electron microscope, J. Periodontal Res., 11, 74-85 (1976). A. H. Meckel, The formation and properties of organic films on teeth, Arch. Oral BioL, 10, 585-597 (1965). W. G. Armstrong, Origin and nature of the acquired pellicle, Proc. Roy. Soc. Med., 61,923-930 (1968).